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The Energy Blog is where all topics relating to The Energy Revolution are presented. Increasingly, expensive oil, coal and global warming are causing an energy revolution by requiring fossil fuels to be supplemented by alternative energy sources and by requiring changes in lifestyle. Please contact me with your comments and questions. Further Information about me can be found HERE.

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April 29, 2006

Holographic Solar

A novel approach to concentrating PV solar is being proposed by Prism Solar Technologies. Instead of using mirrors or lenses to concentrate the sunlight they are using holograms to concentrate the light. Because the system uses fewer solar cells and more efficiently harvests the sunlight, the company believes it can produce systems at a lower cost than competing solar technologies.

The holographic concentrator utilizes a two-stage optical concentrator and silicon PV cells. The holograms spectrally select sunlight and collect and

concentrate the sunlight. The solar cells are interspersed between the holograms as depicted in the cross-section schematic. A layer of holograms -- laser-created patterns that diffract light -- reflects selected frequencies of light to the mirror-like inside surface of the upper transparent glass (their website shows Tefzel) where it continues to be reflected until it reaches a solar cell.

The modules use passive tracking which requires no moving parts. Different holograms in a concentrator module can be designed to focus light from different angles -- so they don't need moving parts to track the sun. This gives greater output in the early morning and late afternoon.

The company's CEO hopes to have the price-per-watt down to $1.50 (U.S.) with its second-generation product, making it more competitive with fossil-fuel-based energy generation. For now, however, the focus is on raising $6 million (U.S.) so manufacturing can start before the end of the year on first-generation modules, which are expected to cost about $2.40 per watt.

A module has been tested at the U.S. Department of Energies National Renewable Energy Laboratory (NREL). Modules also have been installed and field-tested at numerous sites around the U.S. and Japan. The company has been issued two patents on the technology with additional patents under development.

Like other concentrating PV systems one of the advantages of this system is that it uses less silicon than conventional PV modules. The reduction in silicon is limited because the degree of concentration is limited to a factor of 10 compared to lens based systems that can concentrate light by a factor of 100 to 1,000. The system has two other significant advantages in that it reflects only the light frequencies that can be used by the solar cells and the passive tracking ability of the system. Some other concentrating PV systems, such as the Suncube (formerly the Sunball), SolFocus and Sunflower do not require cooling.

Comments

I remember, years ago, a proposal to integrate holographic mirrors into windows, or awnings, to provide indirect indoor lighting. Light incident at inconvenient angles (too high, too low) was reflected onto the ceiling. In some ways, I find that more interesting than holographic solar concentrators.

Still, as I understandi it holographic concentrators introduce the possibility of solid state solar arrays. Point them in the general direction of the sunlight, and they'll efficiently collect energy all day long, without the borderline prohibitive expenses of sun trackers.

The holograms are more expensive, but they don't need to move to follow the sun. Sun tracking hardware (and you can't really do concentrators without it) ends up being a pretty substantial chunk of the overall cost of an installation. The frames are more complicated, and have parts that are both moderately expensive and can wear out.

When I consider something like this, the first thing I look at is cost per KW, and the second thing is, can it pass homeowner associations' architectural standards. For instance, I don't think the SunCube will pass muster in many cases due to the fact it 'stands out' against the typical dark American roof shingles.

At $2.40/KW, it becomes attractive in states with lower incentives, and if the finished product resembles that photo, it has a better chance of blending in unobtrusively. At $1/KW, everyone will want it.

And I am wondering if this hologram design could be adapted to collect dispersed solar radiation from cloud filtered light.

Combined with certain kinds of concentrating collectors it just might. I think my current design would not need this feature though.

10 suns should be possible even with cloud light. And with vacuum tube heat collection the heat portion of the energy collected should be very efficient also.

The hard part to acomplish is adding infrared PV cells, as they are a very low production item still in the experimental stage.

But even with 39% PV solar to electric conversion and the heat collection this design should be very efficient where the heat can be used directly in the building that the panels are mounted on.

As far as collection of solar energy from highways, if tubing is placed in the asphalt surface and a heat collecting medium like oil is used to transport heat to turbine generators operating with refrigerant every mile or so, hooked into the grid, a vast amount of electricity could be generated.

How much of electric transportation could be powered this way with recharging stations along the highway and even induction strips that could recharge cars and power trucks and buses while they are moving down the highway?

Could geothermal heat be pumped back through the tubing to clear snow and restore the road surface to a safe condition and allow energy collection on sunny winter days?

Some new towns in Sweden melt snow off the pavement as a side-effect of putting all the services under a pavement that can be tilted open for access to water, sewerage, power, telecoms, and public heat from a CHP scheme. The waste heat from the pipes keeps the pavement clear in winter.

That Norwegian floating wind generator is fantastic, as well as their underwater generator in the fijord. Looks like a wind generator mounted on the seabed.

The beauty of using ground heat to do the job (around 50 to 60 degrees) is that it would save snow removal energy, cut down road salt, and allow energy collection from highways even in winter.

The idea of nounting solar panels over highways is a good one also, more efficient than simple heat collection, but costlier. I think that this tubing embedded in the asphalt scheme is more apropriate for highways and solar collectors are more apropriate for location on buildings and over parking lots.

Given the complete exploitation of these areas it might be possible to avoid any use of undeveloped land for solar power, and still power civilization (such as it is).

I like the idea of using land that has been devestated by chemical farming for huge wind farms whilst restoring these areas to a natural state. Like a huge prairie restoration/wind farm national park on the northern great plains going international up into Canada.

Advantages of the Prism units - lower cost per watt, no mechanical tracking needed, more likely to pass zoning/covenant standards

The biggest disadvantages I see for the Prism units are higher surface area/watt, and it APPEARS the unit is permanently assembled/fabricated, so when higher efficiency photocells come out you won't be able to swap, as is the case with the SunCubes.

Given the still-good transparency of these panels they could be used as windows on the south sides of buildings. In Vancouver most tall buildings are walls-of-glass. Over-heating in the summer is an issue and these kinds of "windows" would help control it while still allowing good visibility outward. Could make a nice double win.

If they end up looking more or less like what they do in the picture, these guys could make great integrated sun-shades/awnings for the south face of buildings. PVs have already been utilized in a number of places for this application, but the reflective properties and partially see-through aspect of this design would make a great sunshade. (sorry.... I hang out with design students too much...)

this is a cool development and very star wars-y! but most of the comments here are right. cost is a major consideration here. how does this compare with conventional technologies? does it signicantly increase energy output? solar cells have a long stigma which made them unpopular and unrealistic years ago.

All this talk about alternative energies is fine and well but what is the real truth behind it?

What was General Eisenhower really warning us about? What is it about the military-industrial complex that he saw in it that compelled him to make this warning?

The military has dictated the dynamism of the technology sector. GPS and the internet just to name a few.

It is not us nor the free market system that will dictate when America will adopt and use alternative energies effectively in any measurable way that will mitigate its' geopolitical risk to itself but its' military complex that will determine that!

So the question will be not when will America free itself from energy dependence of oil but rather how soon its' military can do so without something bad happening first!

Someone was working on multi-junction cells to cover all the frequencies the sun emits in a way that would generate 40% efficiency. It was a big deal for them to push beyond 37% from two years ago.

Using optical aluminum or silver (94-96%) to concentrate light into a prism (91-94%), and then only using the correct material at each frequency in the rainbow (70-90%) that comes out could reach 60-90% total efficiency.

It cannot, however, be used to dry alkaline gases such as ammonia because it will form addition products. It is used to dry kelp, which is then used to produce soda ash. It can also be added to liquids to remove suspended or dissolved water.

This hologram design could be developed to collect dispersed solar radiation from cloud filtered light. By generating more solar energy, the system will able to function for various works such as water and space heating.